The present invention relates to a process for breaking emulsions and suspensions and means permitting the performance of this process. It is particularly useful in the field of the purification of industrial sewage.
The principle of the invention is based on the formation of microcrystals of aluminium derivatives at the active sites of an adsorbent substance, more particularly a bentonite. This formation of microcrystals makes it possible to limit the swelling of the adsorbent substance in water.
In the present specification the term "emulsion" designates not only any emulsion, but also any suspension.
Hitherto either aqueous solutions of metal salts or powders have been used for the breaking of emulsions, particularly in the treatment of industrial sewage.
Aqueous solutions of metal salts have the disadvantage of forming with most emulsified systems a coalesced phase, i.e. there is creaming of the disperse phase which makes it difficult to separate the phases. Moreover the use of these metal salts always requires a neutralisation of the reaction mass, because acids form by hydrolysis. There are also disperse systems which resist the action of metal salts and which cannot therefore be separated.
Powders, which are more particularly used for the purification of sewage and in particular those described in published German Applications DOS Nos. 2 507 733 and DOS 2 527 987 are essentially formed from adsorbent substances and metal salts. They have numerous disadvantages. In particular, the salts must not have hygroscopic properties, which would cause a premature reaction between the different constituents of the powders and would lead to a significant loss of reactivity. Powders cannot be used in continuously functioning processes in an industrially profitable manner. In particular the operating procedures given in Example 2 of DOS 2 507 733 in which a mixture of aluminum sulphate (12.5 kg) and kaolin (12.5 kg) is suspended in water (100 l) prior to purifying the sewage (10 m.sup.3) do not permit treatment to be carried out on a continuous basis because said mixture gives a gel and there is no microcrystallisation of the active sites of the kaolin.
Finally powders lead to the problem of dust formation and in many cases there is a danger of silicosis for personnel, whilst the use of such powders involves installations with large dimensions due to their limited solubility in the reaction mass.